1. Field of the Invention
The present invention relates to a secondary battery and a method of producing the secondary battery, where the secondary battery is capable of bringing about high capacity and high output.
2. Description of the Related Art
A secondary battery, especially a lithium ion secondary battery ordinarily includes a positive electrode (positive electrode layer), a liquid or a solid electrolytic layer (separator layer) and a negative electrode (negative electrode layer). In this case, a positive electrode active material and a negative electrode active material are mixed with a conductive assistance, a binder and the like and then are applied to a current collector, to thereby form the positive electrode and the negative electrode respectively.
The above lithium ion secondary battery is in need of higher energy density and higher output in the trend of development, with a strategy for thinning the secondary battery. For accomplishing the above thin secondary battery having a light weight, one solution is a polymer battery which is thinned by using an electrolytic part made of solid. Hereinabove, the electrolytic part was so far made of solution.
The above technology is already known in the art. However, performance (characteristic) of the recent secondary battery has been incomparably improved much more than when the above technology was first disclosed.
A polymer battery uses such a technology that a solid polyvinylidene fluoride (PVDF) electrolytic medium is prepared, then the thus prepared is joined with a positive electrode and a negative electrode, then a plasticizer is extracted from an entire cell prime field, then an electrolytic solution is injected, to thereby gelate the entire cell prime field. The above gelation of the entire cell prime field can eliminate a free electrolytic solution from inside the cell. However, using the solid gelling electrolyte causes an insufficient mechanical strength and fails to accomplish a homogenous application of the thin film electrolyte, resulting in lack of practicability.
For solving the above inconveniences, U.S. Pat. No. 7,183,021 B1 {family of Japanese Patent Application Laid-Open No. 2001-43897 (JP2001043897)} discloses a method of using a solid electrolyte in combination with a separator.